This invention relates to drill bit assemblies, specifically drill bit assemblies used in directional drilling. Often in oil, gas, or geothermal drilling applications subterranean formations may dictate drilling along deviated paths to avoid harsh conditions or to improve hydrocarbon production. Methods for deviating tool strings in the prior art include, but are not limited to whipstocks, bent subs, positive displacement motors, and actuators placed in bottom-hole assemblies.
U.S. Pat. No. 4,420,049 to Holbert, which is herein incorporated by reference for all that it contains, discloses directional drilling carried out by orienting and positioning a whipstock having a curved guide surface at a predetermined rotational angle with respect to the desired azimuth so as to compensate for lateral deviation of the original bore or rathole. The curved guide surface of the whipstock is given a radius of curvature in a longitudinal direction corresponding to that of the drainhole section radius and is provided with a concave face in a transverse direction which defines lateral wings along the guide surface to control the advancement of the drilling tool along the desired course and avoid objectionable helixing. Proper orientation and guidance of the drill tool by means of the radius whipstock as described permits accurate determination of the drainhole orientation vertical drill distance between the zenith and nadir of the drainhole as well as the actual drilled depth between those points.
U.S. Pat. No. 5,706,905 to Barr, which is herein incorporated by reference for all that it contains, discloses a modulated bias unit, for use in a steerable rotary drilling system, comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole, and a control valve operable to bring the actuators alternately in succession into and out of communication with a source of fluid under pressure, as the bias unit rotates. The fluid pressure supplied to each actuator may thus be modulated in synchronism with rotation of the drill bit, and in selected phase relation thereto, so that each movable thrust member is displaced outwardly at the same rotational position of the bias unit so as to apply a lateral bias to the unit for the purposes of steering an associated drill bit. To enable the biasing action to be neutralized or reduced there is provided an auxiliary shut-off valve in series with the control valve, which is operable to prevent the control valve from passing the maximum supply of fluid under pressure to the hydraulic actuators.
U.S. Pat. No. 6,581,699 to Chen, et al., which is herein incorporated by reference for all that it contains, discloses a bottom hole assembly for drilling a deviated borehole and includes a positive displacement motor (PDM) or a rotary steerable device (RSD) having a substantially uniform diameter motor housing outer surface without stabilizers extending radially therefrom. In a PDM application, the motor housing may have a fixed bend therein between a first power section and a second bearing section. The long gauge bit powered by the motor may have a bit face with cutters thereon and a gauge section having a uniform diameter cylindrical surface. The gauge section preferably has an axial length at least 75% of the bit diameter. The axial spacing between the bit face and the bend of the motor housing preferably is less than twelve times the bit diameter. According to the method of the present invention, the bit may be rotated at a speed of less than 350 rpm by the PDM and/or rotation of the RSD from the surface.
U.S. Pat. No. 6,116,354 to Buytaert, which is herein incorporated by reference for all that it contains, discloses a rotary steerable system for use in a drill string for drilling a deviated well. The system utilizes a mechanical gravity reference device comprising an unbalanced weight which may rotate independently of the rotation of the drill string so that its heavy portion is always oriented toward the low side of the wellbore and which has an attached magnet. A magnetic switch that rotates as the drill string rotates is activated when its axis coincides with the axis of the magnet, and this activation results in a thrust member or pad being actuated to “kick” the side of the wellbore.